Traffic Signals

Signals should allow adequate crossing time for pedestrians and an adequate clearance interval based upon a maximum walking speed of 3.5 ft/s. In areas where there is a heavy concentration of the elderly or children, a lower speed (typically 3.0 ft/s) should be used in determining pedestrian clearance time.1 In urban areas, signals are often closely spaced, sometimes every block. Timed sequencing of signals may reduce the amount of time allotted per cycle for pedestrian crossings to unsatisfactory lengths. Signals are usually spaced farther apart in suburban or outlying areas, but similar considerations for pedestrian timing should be made. Centralized traffic signal control allows traffic operators to identify signal malfunctions or adjust signal operations to address pedestrian demand spikes in real time. When pedestrian is significant throughout the day, fixed-time signals should be used to consistently allow crossing opportunities. Pedestrian actuation should only be used when pedestrian crossings are intermittent and should be made accessible to pedestrians of all abilities.

Purpose

Traffic signals create gaps in the traffic flow and allow pedestrians to cross the street at locations where pedestrians would otherwise experience excessive delay, difficulties crossing the street, or safety issues. Warrants in the Manual on Uniform Traffic Control Devices (MUTCD) govern the installation of traffic signals, which are based on the number of pedestrians and vehicles crossing the intersection, among other factors. However, judgment must also be used on a case-by-case basis. For example, pedestrian volume must exceed MUTCD thresholds as a requirement to install a traffic signal to address pedestrian activity. If a new facility is being built—a park or recreational path, for example—there will be a new demand, and the signal could be installed in conjunction with the new facility based on projected crossing demand. There may also be latent demand if a destination is not currently accessible, but could become so with new facilities or redesign.1

Considerations

• Where pedestrian traffic is regular and frequent, pedestrian phases should be activated automatically. Pedestrian actuation should only be used when pedestrian crossings are intermittent.
• Signal cycles should be kept short (preferably 90 seconds maximum) to reduce pedestrian delay. Pedestrians are more inclined to ignore signal indications when delay is significant.
• Marked crosswalks at signals encourage pedestrians to cross at the signal and discourage motorists from encroaching into the crossing area. High-visibility crosswalk treatments such as “ladder-bar” or diagonal striping improve the conspicuity of the crossing.
• Though pedestrians may infrequently cross at some intersections, adequate accommodations for pedestrian activity should be provided. Green signal timings should be long enough to allow pedestrians to cross.
• There is always the potential for latent demand at intersections, even if no sidewalks or crosswalks are present. Pedestrians should always be considered in new and modified signal design projects.

Estimated Cost

Signal costs range from $35,000 to $150,000. Annual maintenance costs are approximately $2,000-4,000.

Safety Effects

A summary of studies that have looked at the safety effects of traffic signals can be found here.